vt: always call notifier with the console lock held

Every invocation of notify_write() and notify_update() is performed
under the console lock, except for one case. Let's fix that.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>